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PY6.1-13 | Respiratory Physiology — Practice Quiz
Practice
12 questions · Untimed · Unlimited attempts
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During quiet inspiration, the intrapleural pressure changes from approximately –5 cmH₂O to –8 cmH₂O. This increased negativity is caused by:
A
Contraction of the internal intercostal muscles
B
Expansion of the thoracic cage by diaphragm contraction and external intercostal contraction
✓
C
Active contraction of the abdominal wall muscles
D
Elastic recoil of the chest wall outward during expiration
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Surfactant secreted by Type II pneumocytes primarily prevents alveolar collapse by:
A
Increasing the elastic recoil of the alveolar wall
B
Reducing surface tension at the air-liquid interface, proportionally more in smaller alveoli
✓
C
Increasing the thickness of the respiratory membrane to resist collapse
D
Stimulating smooth muscle contraction in the alveolar walls
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The respiratory membrane across which gas exchange occurs has a total thickness of approximately:
A
5–10 μm
B
0.2–0.5 μm
✓
C
50–100 μm
D
2–5 μm
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A patient with chronic obstructive pulmonary disease (COPD) undergoes spirometry. Which of the following patterns would you expect?
A
Reduced FEV₁, reduced FVC, FEV₁/FVC ratio > 0.8
B
Reduced FEV₁, normal or increased FVC, FEV₁/FVC ratio < 0.7
✓
C
Normal FEV₁, reduced FVC, FEV₁/FVC ratio > 0.8
D
Increased FEV₁, increased FVC, FEV₁/FVC ratio = 0.8
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According to Fick's Law, which of the following changes would MOST increase the rate of oxygen diffusion across the respiratory membrane?
A
Doubling the thickness of the respiratory membrane
B
Halving the surface area of the alveoli
C
Increasing the partial pressure gradient of oxygen across the membrane
✓
D
Decreasing the solubility of oxygen in the membrane
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The oxyhaemoglobin dissociation curve shifts to the RIGHT in the presence of increased:
A
pH and decreased temperature
B
Temperature, PaCO₂, H⁺ concentration, and 2,3-DPG
✓
C
Fetal haemoglobin concentration
D
Carbon monoxide concentration
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The majority of carbon dioxide in the blood is transported as:
A
Dissolved CO₂ in plasma
B
Carbaminohaemoglobin
C
Bicarbonate ions (HCO₃⁻) in plasma
✓
D
Bound to albumin
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A patient with a large pulmonary embolism blocking blood flow to the right lower lobe has hypoxaemia. The V/Q ratio in the affected region is closest to:
A
0 (shunt)
B
0.8 (normal)
C
Infinity (dead space)
✓
D
3.3 (apex-like)
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The most powerful chemical stimulus for increasing ventilation under normal physiological conditions is:
A
Low arterial PO₂ acting on carotid bodies
B
High arterial PCO₂ acting via central chemoreceptors
✓
C
Low arterial pH acting on aortic bodies
D
High arterial PO₂ acting on medullary centres
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The Hering-Breuer inflation reflex is triggered by stretch receptors in the bronchial walls. The afferent pathway of this reflex travels via the:
A
Phrenic nerve (C3, C4, C5)
B
Glossopharyngeal nerve (CN IX)
C
Vagus nerve (CN X)
✓
D
Intercostal nerves (T1–T11)
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A patient is breathing rapidly and shallowly: tidal volume 200 mL, respiratory rate 30/min, anatomical dead space 150 mL. Their alveolar ventilation is:
A
6,000 mL/min
B
4,500 mL/min
C
1,500 mL/min
✓
D
3,000 mL/min
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A patient with carbon monoxide (CO) poisoning has a PaO₂ of 100 mmHg on arterial blood gas but is severely cyanotic with tissue hypoxia. This is because:
A
CO increases the oxygen-carrying capacity of haemoglobin
B
CO binds haemoglobin with 250× the affinity of O₂ and LEFT-shifts the ODC, preventing O₂ unloading at tissues
✓
C
CO directly inhibits the respiratory centres in the medulla
D
CO reduces dissolved O₂ in plasma by competing for solubility
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